The present invention relates to an image reader and an image forming apparatus having an image reading function.
Image readers project light onto an original sheet and detect the amount of the reflected light in every pixel to be read for determining image density (gradation). In image reading, an error is generated in the read density due to various factors.
Disclosed in JP H10-322555 A is a technique for detecting the amount of irregular reflection light in order to correct an error caused by glossiness of an original sheet page. Disclosed in JP 2002-192815 A are a technique for providing two reading means in order to achieve reading of both sides of an original sheet page, and a technique for compensating a difference in read sensitivity between two surfaces. Disclosed in JP 2005-33465 A is a technique for providing a CIS (Contact Image Sensor) in order to read the back side of an original sheet.
In the image readers which read the reflected light, a change in the amount of the reflected light is small in a high density range, which causes a problem of low resolution capability for high-density images.